1. Field of the Invention
The present invention relates to an improved electronic tagging device for use in a monitoring system designed to indicate an alarm condition when a monitored object or person leaves a predefined area, or when the transmitter housing or strap has been tampered with or removed. The tamper detect monitoring system includes an electronic transmitter, housed in the device, which is attached to the person or equipment being monitored and an alarm notification base unit which indicates an alarm condition whenever the transmitter is removed from within a predefined space around the base unit. The transmitter sends an alarm condition indicating a tamper if the attaching strap is cut. The present invention relates specifically to an improved means for attaching and securing the tagging device, for effecting its activation, and for ensuring that a tamper event is detected while reducing false tamper indications. The device retains physical evidence of the tamper event which may be used in a court of law.
2. Description of the Related Art
Electronic monitoring devices are known in the art. Most employ an electronic transmitter which emits a radio signal and is securely fastened to the monitored person or item. The transmitter or "tag" can transmit its signal only over a limited range. The signal receiver is housed in a base unit located within the confinement area of the item or person. When the base unit does not receive a transmitted signal from the tag, an alarm condition is indicated. A signal is relayed to a remote station which may be a centralized monitoring station, an in-house monitoring station, or a hand-carried monitoring and tracking device. One example of this basic configuration is disclosed in U.S. Pat. No. 4,598,272 to Cox.
Various means of attaching the tag to the monitoree exist: U.S. Pat. No. 4,694,284, issued to Leville et al., discloses a hinged collar; U.S. Pat. No. 4,973,944, issued to Maletta describes a transmitter attached via a wrist band. By far, the most common method of attachment employs a strap which can be wrapped around and securely attached to an appendage of the monitoree. One such strap is disclosed in U.S. Pat. No. 4,812,823 issued to Dickerson.
The prior art also describes various methods for relaying an alarm condition to monitoring personnel from the monitoree's remote location. One such method as disclosed in U.S. Pat. No. 4,980,671, issued to McCurdy, teaches connecting the base monitoring unit to a telephone network for placing a telephone call to monitoring personnel whenever an alarm condition is detected. U.S. Pat. No. 5,255,306, issued to Melton et al., makes use of a cellular based telephone system in order to contact the monitoring personnel. It is also known in the art for each transmitting tag to include information such as a unique identifier for the monitoree, an indication that the tag has been tampered with, etc., in the transmitted signal as disclosed in U.S. Pat. No. 5,189,395, issued to Mitchell. Whereas each of these prior art devices discloses one or more features commonly found on electronic monitoring devices (i.e., a strap arrangement for securing the transmitter to a person or a piece of property, an identifiable signal emitted by the transmitter under certain circumstances, alteration of the signal upon certain movement of the person or equipment or upon tampering with the device), electronic monitoring systems presently available are not without their problems. Many of the existing systems are fraught with errors in detecting the difference between a false tamper incident and an actual tamper event. Excessive false tamper incidents in many of the existing systems have resulted in tamper condition reports simply being ignored because no physical evidence of a tamper can be observed when monitoring personnel attempt to verify the false tamper.
Another problem in the current state of the art involves the method of the attachment of the tag to the monitoree. Most straps used in the current art to attach the transmitter to the monitoree must be cut to size for each individual monitoree resulting in many differently sized straps for each transmitter and correspondingly increasing their cost. The straps are made more complicated by using mechanical means for physically and electrically attaching the strap to the transmitter housing and the monitoree. The mechanical components are often exposed to the elements allowing opportunities for corrosion and intermittent electrical shorts which increase the number of tamper signal indications when no tamper event actually occurred. These mechanical components include rivets, spike connectors, metal-on-metal screws, screw plates and slide bar connectors.
Current attachment methods dramatically increase the cost of monitoring by constantly reporting false tampers which do not exist. Phone line usage costs are often incurred each time the transmitter signals the false tamper condition by causing the in-home monitoring unit to report to the monitoring center usually by long distance service or 800 number phone line service. There are additional costs incurred when monitoring personnel are dispatched to the location to investigate the cause of the tamper signal. The constant false tamper condition signals reduce the reliability of current devices while increasing the cost of using them. On the other hand, both proper and improper installation of these devices can create opportunities for undetected or cancelable tampers and situations where removal and replacement of the strap cannot be determined by physical inspection. This often causes monitoring personnel to conclude that the tamper condition was false when in fact it was an actual tamper event.
Additional problems in the current state of the art involve the method of activating the transmitter. Many devices require the use of additional expensive electronic activation equipment to enable the radio transmitter and the tamper circuitry. Several current systems use a simple magnet to perform this function. Such magnets are easy to obtain and are easily used to reset or clear a tamper event, thereby deceiving the authorities about an actual tamper.
Further problems in the current state of the art involve the type and structure of the material used to complete the tamper circuit. The entire strap is often made of a conductive material thereby making it possible to use a jumper wire at any point on the strap to maintain the integrity of the circuit while permitting the strap to be severed and removed undetected.
A further problem in the current state of the art is that many of the systems do not have field replaceable batteries. To replace the battery in these systems, the transmitter must be sent back to the factory. This incurs additional costs for shipping as well as delays in the use of the transmitter requiring costly back-up units.
The present invention provides an improved monitoring device which eliminates the exposed strap, mechanical attachment, components thereby eliminating the causes for many of the false tamper incidents. The strap of the present invention is easily attached to and removed from the monitoree by authorized personnel by means of a reusable, size-adjustable and field-replaceable flex circuit strap. No specialized installation tools are required. The strap of the present invention has tamper detection circuitry embedded between layers of poly material with several false circuits to confuse any attempts to jumper the strap and tamper with the system. An inexpensive, replaceable and custom designed latch key serves to both lock the strap in place and activate the transmitter. When the latch key is forcibly removed or cut by unauthorized personnel, it leaves clear and unrefutable physical evidence of a tamper event which can be used in a court of law. The device is equipped with field replaceable batteries which eliminate the need to ship it back to the factory to replace the batteries.